Why is faith good?

This is an honest question from an atheist to those who believe in any kind of religion or more general 'spirituality.' In my debates with religious folks, the word 'faith' comes up rather often. Whenever I bring up my perceived lack of evidence for a particular belief, or logical inconsistency of the argument they use to support a notion, they'll say "People just have to have faith," or something to the effect of "If God showed himself, what would be left to have faith in?" So my question is this: [b]Why is faith something to be valued?[/b] Why should one [i]want[/i] to believe in something for which they have no supporting evidence or argument? How is the act of accepting the truth of a notion despite having no reason to do so beneficial or desirable in any way?